In a storage array, applications access data by providing input/output (I/O) requests based upon logical unit numbers, or LUNs. In some storage arrays, there is more than one storage processor (SP) that may be in use, typically referred to as SPA and SPB. In such a situation, a LUN has as its default owner either SPA or SPB. If a storage processor fails, the remaining SP takes over the LUNs owned by the failed storage processor, which is referred to as trespassing.
A file system may support multiple LUNs, and some of the LUNs may be owned by a storage processor other than the storage processor on which the file system is mounted. I/Os that are received for LUNs that are not owned by the same storage processor as the one on which the file system is mounted are redirected to the other storage processor. Such redirection causes a performance penalty.